1. Field of the Invention
The present invention relates to an apparatus that inspects a panel of a liquid crystal display (LCD).
2. Discussion of the Related Art
Generally, LCD inspection apparatuses are adapted to easily inspect, with the naked eye, whether or not an LCD panel is defective.
FIGS. 1 and 2 illustrate a conventional LCD inspection apparatus. As shown in FIGS. 1 and 2, the conventional LCD inspection apparatus includes a body 1, an inspection stage 2 arranged at one side of the body 1, to perform an inspection of an LCD panel 10, to be inspected, and a loading/unloading stage 7 which is arranged at the other side of the body 1, to load the LCD panel 10, to be inspected, in the inspection stage 2, and to unload the inspected LCD panel 10 from the inspection stage 2.
As seen in FIG. 2, the LCD inspection apparatus includes a carrier 9 which is mounted to the body 1 such that the carrier 9 is laterally movable. The carrier transfer, the LCD panel 10 from the loading/unloading stage 7 to the inspection stage 2, or from the inspection stage 2 to the loading/unloading stage 7.
The inspection stage 2 includes probe units 3, and a worktable 4 which brings the LCD panel 10 into contact with the probe units 3. The worktable 4 also provides light. The worktable 4 includes a polarizing unit 4a and a backlight 4b which are arranged at a front portion of the worktable 4, in this order. A moving stage 5 is arranged at the rear of the worktable 4, and is connected to the probe units 3 in a state of being aligned with the probe units 3.
A sub table 8 is mounted to the loading/unloading stage 7. The sub table 8 functions to incline the LCD panel 10 transferred from a loader (not shown) of the loading/unloading stage 7 by a predetermined angle (for example, 60°).
A microscope 6 is mounted to the body 1 in front of the inspection stage 2 such that the microscope 6 is movable in vertical and lateral directions. When it is determined, in a macroscopic inspection operation, that the LCD panel 10 has defects, the operator can more precisely identify the defects of the LCD panel 10, using the microscope 6.
An inspection procedure carried out in the above-mentioned conventional LCD inspection apparatus will be described in brief.
A LCD panel 10 to be inspected is transferred from the loader (not shown) of the loading/unloading stage 7 to the sub table 8 which, in turn, transfers the LCD panel 10 to the carrier 9 while being inclined by a predetermined angle. Subsequently, the carrier 9 feeds the LCD panel 10 to the inspection stage 2. When the LCD panel 10 is placed in the inspection stage 2, the worktable 4 is moved toward the LCD panel 10 in accordance with operation of the moving stage 5. The worktable 4 vacuum-chucks the LCD panel 10 such that the LCD panel 10 is maintained in a fixed state, and then connects pads (not shown) of the fixed LCD panel 10 to lead pins (not shown) of the probe units 3, respectively.
When electrical connection is achieved between the LCD panel 10 and the probe units 3, as mentioned above, a predetermined image signal from a pattern generator is input to the LCD panel 10 via the probe units 3. The pattern generator, which is an external image signal input unit, sequentially provides various image patterns. When the LCD panel 10 is illuminated by the backlight 4b, such various image patterns are sequentially displayed on the LCD panel 10. Accordingly, the operator can determine whether or not the LCD panel 10 is defective, through the displayed patterns.
As shown in FIG. 3A, the polarizing unit 4a of the above-mentioned conventional LCD inspection apparatus includes a polarizing plate 42, a diffusing plate 43, and a light guide plate 44 which are laminated over one another in a uniformly-spaced state.
In the polarizing unit 4a having the above-mentioned structure the diffusing plate 43 may be expanded due to hot air generated during light emission of the backlight unit 4b carried out in an inspection of the LCD panel 10, as shown in FIG. 3B. Due to the expansion of the diffusing plate 43, non-uniform gap regions “a” are formed in gaps between the diffusing plate 43 and the polarizing plate 42 and between the diffusing plate 43 and the light guide plate 44. Such non-uniform gap regions “a” may be exhibited in the form of stains in an image displayed on the LCD panel 10 in the inspection of the LCD panel 10.
Boundary regions of stains present in an image displayed on the LCD panel 10 in an inspection of the LCD panel 10 are excluded from inspection regions. This is because the stain boundary regions are detected as defects.
Since no inspection is carried out for the stain boundary regions, there is a problem in that it is impossible to detect substantial defects, for example, point defects (PDs) or line defects (LDs), present in the stain boundary regions.
In order to detect substantial defects present in the non-inspected regions, an additional precise inspection must be carried out for the non-inspected regions. In this case the total task time (namely, the total inspection time for the LCD panel) is increased.